In recent years, samples are frequently processed using a high-energy charged particle beam (e.g., focused ion beam). For example, a known technique for finely processing a sample is as follows. A charged particle beam is extracted from a charged particle source by an extracting electrode. The extracted charged particle beam is accelerated by an earth electrode (acceleration electrode) and finely focused by a lens so that the sample is irradiated with the beam (refer to Patent Document 1 and the like).